my head canon

one time dazai and chuuya were married but dazai didn't love chuuya so dazai secretly dated fyodor. chuuya didn't know for a long time but he found out so he poisoned dazai who died. dazai turned into Cassidy from FNAF (five nights at Freddy's) and wanted revenge on chuuya so he went to find him. Mori adopted him and dazai found Chuuya and wanted Fyodor back but Fyodor turned into s demon which changed everything.